Refrigerant compressor, cooling system and refrigerator

ABSTRACT

A refrigerant compressor having a compression element comprising sliding components made of metallic materials, wherein a mixed layer is formed by solid-dissolving molybdenum disulfide in at least one of the sliding faces of the sliding components, and a single molybdenum disulfide layer is further formed on the surface of the mixed layer. With this configuration, initial break-in is done using the single layer, and sliding loss is reduced. Even if the single layer peels off, because the molybdenum disulfide of the mixed layer is cleaved at a low friction coefficient, solid lubrication action is attained, the friction coefficient of the sliding section is lowered, and sliding loss is reduced.

TECHNICAL FIELD

The present invention relates to a refrigerant compressor being usedmainly for household electric refrigerator-freezers and the like.

BACKGROUND ART

In recent years, highly efficient compressors consuming less fossil fuelhave been being developed for the protection of global environment.

In a conventional compressor, one of the sliding members constituting asliding section is made of a nitrided iron-based material treated withmanganese phosphate, and the other sliding member is made of anodizedaluminum die cast (for example, refer to Japanese Patent ApplicationLaid-open No. Hei 6-117371).

FIG. 14 is a sectional view showing a conventional refrigerantcompressor disclosed in Japanese Patent Application Laid-open No. Hei6-117371. As shown in FIG. 14, in a closed container 1, oil 2 isaccumulated at the bottom thereof, and the closed container 1accommodates an electric driving element 5 comprising a stator 3 and arotor 4, and also accommodates a reciprocating compression element 6that is driven using the electric driving element 5.

Next, the details of the compression element 6 will be described below.

A crankshaft 7 comprises a main shaft section 8 on which the rotor 4 ispressure-fitted so as to be secured thereto and an eccentric shaft 9formed so as to be eccentric with respect to the main shaft section 8.The crankshaft 7 is provided with an oil pump 10. A compression chamber13 having a nearly cylindrical bore section 12 is formed in a cylinderblock 11, and the cylinder block 1 is provided with a bearing section 14for journaling the main shaft section 8.

A piston 15, loosely fitted in the bore section 12, is connected to theeccentric shaft 9 via a piston pin 16 and a connecting rod 17 serving asa connecting means. The end face of the bore section 12 is sealed with avalve plate 18.

A head 19 in which a high-pressure chamber is formed is secured to thevalve plate 18 on the opposite side of the bore section 12. A suctiontube 20 is secured to the closed container 1 and connected to thelow-pressure side (not shown) of a refrigerating cycle so as tointroduce refrigerant gas (not shown) into the closed container 1. Asuction muffler 21 is held between the valve plate 18 and the head 19.

Sliding sections are respectively formed between the main shaft section8 of the crankshaft 7 and the bearing section 14, between the piston 15and the bore section 12, between the piston pin 16 and the connectingrod 17, and between the eccentric shaft 9 of the crankshaft 7 and theconnecting rod 17. One of the sliding members constituting the slidingsection is made of a nitrided iron-based material treated with manganesephosphate, and the other sliding member is made of anodized aluminum diecast.

The operation of the refrigerant compressor configured as describedabove will be described next. The power supplied from the commercialpower supply (not shown) is supplied to the electric driving element 5to rotate the rotor 4 of the electric driving section 5. The rotor 4rotates the crankshaft 7, and the eccentric operation of the eccentricshaft 9 is transmitted from the connecting rod 17 serving as aconnecting means to the piston pin 16 to drive the piston 15. Hence, thepiston 15 reciprocates inside the bore section 12, and the refrigerantgas introduced into the closed container 1 through the suction tube 20is sucked through the suction muffler 21 and compressed continuouslyinside the compression chamber 13.

As the crankshaft 7 is rotated, the oil 2 is supplied from the oil pump10 to the respective sliding sections to lubricate the sliding sections.In addition, the oil 2 supplied serves as a seal between the piston 15and the bore section 12.

The piston 15 is loosely fitted in the bore section 12 while a verysmall clearance is provided therebetween to reduce leakage loss. As aresult, the piston 15 and the bore section 12 may make partial contactwith each other owing to fluctuations in shape and accuracy thereof.However, because one of the sliding members in the sliding section istreated with manganese phosphate that is low in hardness and density,even if they make contact with each other, the manganese phosphate atthe contact portion is abraded, whereby the shapes of the two matingmembers can be adapted to each other (initial break-in). Hence, slidingloss can be reduced at the sliding section between the piston 15 and thebore section 12.

In the refrigerant compressor described in the above-mentioned JapanesePatent Application Laid-open No. Hei 6-117371, because one of thesliding members in the sliding section is treated with manganesephosphate that is low in hardness and density, the sliding section hasgood initial break-in performance. However, for example, if the slidingmembers make contact with each other repeatedly at the time of startupor the like during which no oil film is formed between the slidingmembers, the manganese phosphate layer is abraded and lost, and the basematerials of the sliding members may make metallic contact with eachother. As a result, the friction coefficient rises and sliding lossincreases in the refrigerant compressor. If the heat generated from thesliding members increases, abrasion may increase and abnormal abrasionmay occur.

If abrasion occurs between the piston 15 and the bore section 12 inparticular, the clearance therebetween increases, the compressedrefrigerant gas may leak from the clearance between the piston 15 andthe bore section 12, and the efficiency may be lowered.

In addition, metal powder generated by the abrasion reacts with degradedsubstances in the oil, and sludge is formed. This sludge adheres to theinner wall of a capillary tube having a minute flow path, and anexpansion valve, being generally used as an expander in a coolingsystem, and may inhibit the circulation of the refrigerant.

Furthermore, according to another conventional technology, a mixed layeris formed by solid-dissolving molybdenum disulfide (MoS₂) serving as asolid lubricant in the sliding surface of the sliding member so as tofunction as a sliding material for a compressor (for example, refer tothe pamphlet of WO 04/055371).

FIG. 15 shows the cross-section of a mixed layer formed bysolid-dissolving molybdenum disulfide according to the conventionaltechnology described in the pamphlet of WO 04/055371.

As shown in FIG. 15, a mixed layer 33 is formed by solid-dissolvingmolybdenum disulfide in the sliding face of a sliding component that ismade of a metallic material and constitutes a compression element. Withthis configuration, even if metallic contact occurs between the piston15 and the bore section 12 at the top dead center and the bottom deadcenter of the piston 15 wherein the speed of the piston 15 becomes zero,the friction coefficient is lowered owing to the solid lubrication ofthe molybdenum disulfide in the mixed layer 33 formed on the surface ofthe piston 15, and friction loss can be reduced. Furthermore, minutepits 34 formed in the surface of the sliding section serve as labyrinthseals during compression, whereby leakage loss can be reduced andabrasion resistance can be improved.

According to the specifications described in the pamphlet of theabove-mentioned WO 04/055371, even if solid-to-solid contact occurs, themolybdenum disulfide of the mixed layer 33 is cleaved at low frictioncoefficient, and self-lubrication action is achieved. However, accordingto the specifications, the mixed layer has hardness close to that of thebase material, and the effect of initial break-in is hardly obtained.Hence, sliding loss cannot be reduced, and there is a problem oflowering the efficiency of the compressor.

Additionally, although the mixed layer has self-lubrication action, ifthe mixed layer or the sliding face of the mating sliding component isabraded, there is a problem of generating metal powder and metallicsalts.

For example, in the case that a mixed layer is formed bysolid-dissolving molybdenum disulfide in a sliding face, as described inthe pamphlet of WO 04/055371, and that the manganese phosphate treatmentdescribed in Japanese Patent Application Laid-open No. Hei 6-117371 isfurther carried out on the mixed layer, it is conceived that theadvantages of using the two methods are obtained. However, if themanganese phosphate treatment is carried out on the mixed layer, thesurface of the sliding component and the mixed layer formed bysolid-dissolving molybdenum disulfide in the surface are corroded andlost because of the chemical reactions carried out during the manganesephosphate treatment according to the chemical reaction formulas:(chemical formula 1), (chemical formula 2) and (chemical formula 3)described below. For this reason, it is almost impossible to realize theconfiguration described above.

2H₃PO₄+Fe→Fe(H₂PO₄)₂+H₂  (Chemical formula 1)

Me(H₂PO₄)₂→MeHPO₄+H₃PO₄  (Chemical formula 2)

3MeHPO₄→Me₃(PO₄)₂+H₃PO₄  (Chemical formula 3)

where Me is a divalent metallic salt (Fe, Mn), Me(H₂PO₄)₂ is a primaryphosphate, MeHPO₄ is a secondary phosphate, and Me₃(PO₄)₂ is a tertiaryphosphate.

DISCLOSURE OF THE INVENTION

The present invention has been made to solve the conventional problemsdescribed above, and is intended to provide a refrigerant compressorbeing capable of reducing sliding loss and having high reliability andhigh efficiency.

For the purpose of solving the conventional problems described above, arefrigerant compressor according to the present invention ischaracterized in that a mixed layer is formed by solid-dissolvingmolybdenum disulfide in at least one of the sliding faces of the slidingcomponents made of metallic materials, and a single molybdenum disulfidelayer is further formed on the surface of the mixed layer. With thisconfiguration, initial break-in is done using the single molybdenumdisulfide layer. This produces effects of reducing sliding loss,suppressing abrasion on the base material and the mixed layer or thesliding face of the mating sliding component, and preventing generationof metal powder. Furthermore, in the refrigerant compressor according tothe present invention, even if the single layer peels off andsolid-to-solid contact occurs, because the molybdenum disulfide of themixed layer has a hexagonal closed packing crystal structure, themolybdenum disulfide is cleaved at a low friction coefficient, wherebysolid lubrication action is attained. This produces effects of loweringthe friction coefficient of the sliding component and reducing slidingloss.

In the refrigerant compressor according to the present invention, amixed layer is formed by solid-dissolving molybdenum disulfide in asliding face, and a single molybdenum disulfide layer is further formedon the surface of the mixed layer as described above. With thisconfiguration, the friction coefficient can be reduced, and it ispossible to provide a refrigerant compressor having high reliability andhigh efficiency. Furthermore, in the refrigerant compressor according tothe present invention, it is possible to suppress generation of metalabrasion powder from the mixed layer, the base material and the slidingface of the mating sliding component. Hence, the amounts of metallicsalts formed by the reaction between the metal abrasion powder anddegraded oil are reduced. As a result, even if the refrigerant pathshave minute paths, such as a capillary tube and an expansion valve, theminute paths can be prevented from being clogged with metallic salts.

An invention set forth in claim 1 is characterized in that a compressionelement comprises sliding components made of metallic materials, andthat a mixed layer is formed by solid-dissolving molybdenum disulfide inat least one of the sliding faces of the sliding components, and asingle molybdenum disulfide layer is further formed on the surface ofthe mixed layer. With this configuration, the friction coefficient islowered by the self-lubrication action of the molybdenum disulfide ofthe single molybdenum disulfide layer. This produces an effect ofreducing sliding loss. Furthermore, according to the invention set forthin claim 1, even if the single layer peels off and solid-to-solidcontact occurs, because the molybdenum disulfide of the mixed layer hasa hexagonal closed packing crystal structure, the molybdenum disulfideis cleaved at a low friction coefficient, whereby solid lubricationaction is attained. This lowers the friction coefficient of the slidingcomponent and reduces sliding loss. Hence, according to the inventionset forth in claim 1, it is possible to suppress metal abrasion on themixed layer, the base material and the sliding face of the matingsliding component, whereby it is possible to provide a refrigerantcompressor having high reliability and high efficiency.

An invention set forth in claim 2 is characterized in that the maximumconcentration of the molybdenum disulfide in the mixed layer accordingto the invention set forth in claim 1 is 5 wt % or more. Hence, theself-lubrication of the molybdenum disulfide of the mixed layer isstabilized, and the friction coefficient is lowered further. For thisreason, according to the invention set forth in claim 2, it is possibleto suppress metal abrasion on the mixed layer, the base material and thesliding face of the mating sliding component, in addition to the effectsof the invention set forth in claim 1, whereby it is possible to providea refrigerant compressor having high reliability and high efficiency.

An invention set forth in claim 3 is characterized in that the thicknessof the mixed layer according the invention set forth in claim 1 is 0.1to 2.0 μm. By the setting of the thickness of the mixed layer at 0.1 to2.0 μm, the solid lubrication action of the molybdenum disulfide of themixed layer can be attained stably. Hence, according to the inventionset forth in claim 3, the friction coefficient of the sliding componentis lowered, and sliding loss can be reduced. For this reason, accordingto the invention set forth in claim 3, it is possible to suppress metalabrasion on the mixed layer, the base material and the sliding face ofthe mating sliding component, in addition to the effects of theinvention set forth in claim 1, whereby it is possible to provide arefrigerant compressor having high reliability and high efficiency.

An invention set forth in claim 4 is characterized in that the purity ofthe molybdenum disulfide of the single molybdenum disulfide layeraccording to the invention set forth in claim 1 is 98% or more. Hence,the amounts of impurities having friction coefficients higher than thatof the molybdenum disulfide become very small, whereby the frictioncoefficient of the single molybdenum disulfide layer can be lowered, andsliding loss can be reduced. For this reason, according to the inventionset forth in claim 4, it is possible to suppress metal abrasion on themixed layer, the base material and the sliding face of the matingsliding component, in addition to the effects of the invention set forthin claim 1, whereby it is possible to provide a refrigerant compressorhaving high reliability and high efficiency.

An invention set forth in claim 5 is characterized in that the thicknessof the single molybdenum disulfide layer according to the invention setforth in claim 1 is 0.1 to 2.0 μm. Even if the single layer having athickness of 0.1 to 2.0 μm peels off, the amount of leakage from betweenthe piston and the bore section does not increase excessively, andfreezing capacity is not lowered. For this reason, according to theinvention set forth in claim 5, it is possible to provide a refrigerantcompressor having higher efficiency, in addition to the effects of theinvention set forth in claim 1.

An invention set forth in claim 6 provides the refrigerant compressorset forth in any one of claims 1 to 5, wherein oil is accumulated and acompression element is accommodated in a closed container, thecompression element is a reciprocating compression element comprising acrankshaft equipped with a main shaft and an eccentric shaft; a thrustsection, one end of which is integrated with the crankshaft and theother end of which is integrated with a bearing section; the bearingsection rotatably journaling the main shaft; a cylinder block in which acylindrical bore section is formed; a piston reciprocating inside thecylindrical bore section; a piston pin disposed in parallel with theeccentric shaft and secured to the piston; and a connecting rod forconnecting the eccentric shaft to the piston, and the sliding componentmade of a metallic material is at least either one of the crankshaft,the thrust section, the cylinder block, the piston, the piston pin, andthe connecting rod. With this configuration of the invention set forthin claim 6, initial break-in is done using the single molybdenumdisulfide layer. This produces an effect of reducing sliding loss. Evenif the single layer peels off and solid-to-solid contact occurs, becausethe molybdenum disulfide of the mixed layer has a hexagonal closedpacking crystal structure, the molybdenum disulfide is cleaved at a lowfriction coefficient, whereby solid lubrication action is attained. Thisproduces effects of lowering the friction coefficient of the slidingcomponent and reducing sliding loss. For this reason, according to theinvention set forth in claim 6, it is possible to suppress metalabrasion on the mixed layer, the base material and the sliding face ofthe mating sliding component, whereby it is possible to provide arefrigerant compressor comprising a reciprocating compression elementand having high reliability and high efficiency.

An invention set forth in claim 7 provides the refrigerant compressoraccording to the invention set forth in any one of claims 1 to 5,wherein oil is accumulated and a compression element is accommodated ina closed container, the compression element comprises a crankshaftequipped with a main shaft and an eccentric shaft; a thrust section, oneend of which is integrated with the crankshaft and the other end ofwhich is integrated with a bearing section; the bearing sectionrotatably journaling the main shaft; a cylinder block in which acylindrical bore section is formed; a piston reciprocating inside thecylindrical bore section; and a connecting rod to which a ball issecured on the side connected to the piston, the piston in which theball is movably held by crimping constitutes a reciprocating compressionelement, and the sliding component made of a metallic material is atleast either one of the crankshaft, the thrust section, the cylinderblock, the piston, and the connecting rod. With this configuration ofthe invention set forth in claim 7, initial break-in is done using thesingle molybdenum disulfide layer. This produces an action of reducingsliding loss. Even if the single layer peels off and solid-to-solidcontact occurs, because the molybdenum disulfide of the mixed layer hasa hexagonal closed packing crystal structure, the molybdenum disulfideis cleaved at a low friction coefficient, whereby solid lubricationaction is attained. This produces effects of lowering the frictioncoefficient of the sliding component and reducing sliding loss. For thisreason, according to the invention set forth in claim 7, it is possibleto suppress metal abrasion on the mixed layer, the base material and thesliding face of the mating sliding component. As a result, the amount ofmetal abrasion powder that enters the crimped section between the pistonand the ball and is trapped therebetween is reduced. Hence the freemovement of the ball cannot be restricted, and it is possible to providea reciprocating refrigerant compressor comprising a reciprocatingcompression element and having high reliability and high efficiency.

An invention set forth in claim 8 provides the refrigerant compressoraccording to the invention set forth in any one of claims 1 to 5,wherein oil is accumulated and a compression element is accommodated ina closed container, the compression element is a rolling-piston-typecompression element comprising a shaft having an eccentric section; acylinder in which a compression chamber is formed in coaxial with therotation center of the shaft; a rolling piston that is loosely fitted onthe eccentric section and rolls inside the compression chamber; a vanethat partitions the compression chamber into the high-pressure side andthe low-pressure side thereof when made contact with the rolling pistonunder pressure; a main bearing and an auxiliary bearing that are used toseal both end faces of the cylinder and to journal the shaft on the sideof an electric driving element and on the opposite side of the electricdriving element, respectively; an oil supply spring secured to one endof the shaft; and an oil supply pipe that accommodates the oil supplyspring and one end of which is open and immersed in the oil, and thesliding component made of a metallic material is at least either one ofthe shaft, the cylinder, the rolling piston, the vane, the main bearing,the auxiliary bearing, the oil supply spring and the oil supply pipe.With this configuration of the invention set forth in claim 8, initialbreak-in is done using the single molybdenum disulfide layer. Thisproduces an effect of reducing sliding loss. Even if the single layerpeels off and solid-to-solid contact occurs, because the molybdenumdisulfide of the mixed layer has a hexagonal closed packing crystalstructure, the molybdenum disulfide is cleaved at a low frictioncoefficient, whereby solid lubrication action is attained. This produceseffects of lowering the friction coefficient of the sliding componentand reducing sliding loss. For this reason, according to the inventionset forth in claim 8, it is possible to suppress metal abrasion on themixed layer, the base material and the sliding face of the matingsliding component. It is therefore possible to provide a refrigerantcompressor comprising a rotary compression element and having highreliability and high efficiency.

An invention set forth in claim 9 provides a cooling system comprisingthe refrigerant compressor set forth in any one of claims 1 to 8, and anexpander equipped with either a capillary tube or an expansion valve.According to the invention set forth in claim 9, the amount of metalabrasion powder discharged from the compressor is small, and the amountsof metallic salts formed by the reaction between the metal abrasionpowder and degraded oil and adhering to the inner wall of the capillarytube serving as a minute path and the minute paths inside the expansionvalve are reduced. Hence, the circulation of the refrigerant is notobstructed, and it is possible to provide a cooling system having highreliability.

An invention set forth in claim 10 provides a refrigerator, such as ahousehold refrigerator, having a cooling system comprising therefrigerant compressor set forth in any one of claims 1 to 8, and anexpander equipped with either a capillary tube or an expansion valvethat is more minute than those of general-purpose refrigeratedwarehouses and industrial refrigerators having large amounts ofrefrigerant circulation. Because the invention set forth in claim 10 hasthe cooling system set forth in claim 9, the amount of metal abrasionpowder discharged from the compressor is small, and the amounts ofmetallic salts formed by the reaction between the metal abrasion powderand degraded oil and adhering to the inner wall of the capillary tubeserving as a minute path and the minute paths inside the expansion valveare reduced. Hence, the circulation of the refrigerant is notobstructed, and it is possible to provide a household refrigeratorhaving high reliability, for example.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a refrigerant compressor according toEmbodiment 1 of the present invention;

FIG. 2 is a magnified view of portion A in FIG. 1;

FIG. 3 is a magnified view of portion B in FIG. 2;

FIG. 4 is a view showing how molybdenum disulfide is formed according toEmbodiment 1 of the present invention;

FIG. 5 is a characteristic graph showing the relationship between thefreezing capacity and the clearance between the piston and the boresection of the refrigerant compressor according to Embodiment 1 of thepresent invention;

FIG. 6 is a view showing the concentration distribution of molybdenumdisulfide according to Embodiment 1 of the present invention;

FIG. 7 is a characteristic graph showing the relationship between theconcentration of molybdenum disulfide and the efficiency according toEmbodiment 1 of the present invention;

FIG. 8 is a connecting rod assembly drawing showing a ball secured to aconnecting rod and connected to a piston by crimping so as to be movablefreely according to Embodiment 1 of the present invention;

FIG. 9 is a view showing the configuration of a household refrigeratoraccording to Embodiment 1 of the present invention;

FIG. 10 is a sectional view showing an expansion valve according toEmbodiment 1 of the present invention;

FIG. 11 is a sectional view showing a refrigerant compressor accordingto Embodiment 2 of the present invention;

FIG. 12 is a sectional view taken on line C-D in FIG. 11;

FIG. 13 is a magnified view of portion E in FIG. 12;

FIG. 14 is a sectional view showing the conventional refrigerantcompressor; and

FIG. 15 is a sectional view showing the conventional mixed layer formedby solid-dissolving molybdenum disulfide.

BEST MODES FOR CARRYING OUT THE INVENTION Embodiment 1

FIG. 1 is a sectional view showing a refrigerant compressor according toEmbodiment 1 of the present invention, FIG. 2 is a magnified view ofportion A in FIG. 1, FIG. 3 is a magnified view of portion B in FIG. 2,FIG. 4 is a view showing how molybdenum disulfide is formed according toEmbodiment 1, FIG. 5 is a characteristic graph showing the relationshipbetween the freezing capacity and the clearance between the piston andthe bore section of the refrigerant compressor according to Embodiment1, FIG. 6 is a view showing the concentration distribution of molybdenumdisulfide according to Embodiment 1, FIG. 7 is a characteristic graphshowing the relationship between the concentration of molybdenumdisulfide and the efficiency according to Embodiment 1, FIG. 8 is aconnecting rod assembly drawing showing a ball secured to a connectingrod and connected to a piston by crimping so as to be movable freelyaccording to Embodiment 1, FIG. 9 is a view showing the configuration ofa household refrigerator according to Embodiment 1, and FIG. 10 is asectional view showing an expansion valve according to Embodiment 1.

In FIGS. 1, 2 and 3, a closed container 101 is filled with refrigerantgas 102, R600a, and oil 103 is accumulated at the bottom of the closedcontainer 101. Furthermore, the closed container 101 accommodates anelectric driving element 106 comprising a stator 104 and a rotor 105,and also accommodates a reciprocating compression element 107 that isdriven using the electric driving element 106.

The details of the compression element 107 will be described below.

A crankshaft 108 comprises a main shaft 109 on which the rotor 105 ispressure-fitted so as to be secured thereto and an eccentric shaft 110formed so as to be eccentric with respect to the main shaft 109. An oilpump 111 communicating with the bottom of the closed container 101 inwhich the oil 103 is accumulated is provided at the lower end of thecrankshaft 108. A nearly cylindrical bore section 113 is formed in acylinder block 112 made of cast iron, and the cylinder block 112 isprovided with a bearing section 114 for journaling the main shaft 109.

In addition, a flange face 120 is formed on the rotor 105, and a thrustsection 122 is formed on the upper end face of the bearing section 114.A thrust washer 124 is inserted between the flange face 120 and thethrust section 122 of the bearing section 114. The flange face 120, thethrust section 122 and the thrust washer 124 constitute a thrust bearingsection 126.

A piston 132 made of an iron-based material is loosely fitted in thebore section 113 while having a constant clearance therebetween. Thepiston 132 and the bore section 113 form a compression chamber 134. Thepiston 132 is connected to the eccentric shaft 110 via a piston pin 137and a connecting rod 138 serving as a connecting means. The end face ofthe bore section 113 is sealed with a valve plate 139.

A head 140 in which a high-pressure chamber is formed is secured to thevalve plate 139 on the opposite side of the bore section 113. A suctiontube (not shown) is secured to the closed container 101 and connected tothe low-pressure side (not shown) of a refrigerating cycle so as tointroduce refrigerant gas 102 into the closed container 101. A suctionmuffler 142 is held between the valve plate 139 and the head 140.

Sliding sections are respectively formed between the piston 132 and thebore section 113, between the main shaft 109 and the bearing section114, between the thrust section 122 and the thrust washer 124, betweenthe piston pin 137 and the connecting rod 138, and between the eccentricshaft 110 and the connecting rod 138. In at least one of the slidingmembers constituting the sliding section, a mixed layer 150 is formed bysolid-dissolving molybdenum disulfide in the surface of the basematerial, and a single molybdenum disulfide layer 160 is further formedon the surface of this mixed layer 150.

The configuration of the sliding member will be described below indetail, taking the piston 132 as an example.

In the sliding section provided between the piston 132 and the boresection 113, the mixed layer 150 is formed by solid-dissolvingmolybdenum disulfide in the sliding surface of the piston 132, that is,the surface of an iron-based material serving as the base materialthereof, and the single molybdenum disulfide layer 160 is further formedon the surface of the mixed layer 150. It is preferable that the purityof the molybdenum disulfide should be 98% or more, that the thickness ofthe single molybdenum disulfide layer 160 should be 0.1 to 2.0 μm, thatthe thickness of the mixed layer 150 should be 0.1 to 2.0 μm, and thatthe maximum concentration of the molybdenum disulfide in the mixed layer150 should be 5 wt % or more and 50 wt % or less.

As a method for forming the mixed layer 150 in which molybdenumdisulfide is solid-dissolved and further forming the single molybdenumdisulfide layer 160 on the surface of the mixed layer 150, a method forcolliding the particles of molybdenum disulfide having a purity of 98%or more with the sliding face made of a metal serving as the basematerial of a sliding component at a speed of a certain level or more isused in Embodiment 1 of the present invention.

It is preferable that the projection pressure of molybdenum disulfide atthis time should be 1.0 to 1.5 MPa. With this method, the oxygen in thesurface of the base material is diffused using the thermal energygenerated during the collision, and the single molybdenum disulfidelayer 160 is formed. In addition, by the collision of the particles ofmolybdenum disulfide, some of the particles are melted into the basematerial and bonded metallically. As a result, it is found that themixed layer 150 in which molybdenum disulfide is solid-dissolved and thesingle molybdenum disulfide layer 160 can be formed simultaneously.

The piston 132 is loosely fitted in the bore section 113 while a verysmall clearance of approximately 5 to 15 μm for example in a diametricdirection is provided therebetween to reduce leakage loss.

The operation of the refrigerant compressor according to Embodiment 1configured as described above will be described below.

The power supplied from the commercial power supply (not shown) issupplied to the electric driving element 106 to rotate the rotor 105 ofthe electric driving element 106. By the rotation of the rotor 105, thecrankshaft 108 is rotated, and the eccentric shaft 110 is rotatedeccentrically. The eccentric operation of the eccentric shaft 110 istransmitted from the connecting rod 138 serving as a connecting means tothe piston pin 137 to drive the piston 132. Hence, the piston 132reciprocates inside the bore section 113. As a result, the refrigerantgas 102 introduced into the closed container 101 through the suctiontube (not shown) is sucked through the suction muffler 142 andcompressed inside the compression chamber 134.

As the crankshaft 108 is rotated, the oil 103 is supplied from the oilpump 111 to the respective sliding sections to lubricate the slidingsections. In addition, the oil 103 supplied serves as a seal between thepiston 132 and the bore section 113.

Because the clearance between the piston 132 and the bore section 113 isvery small, the piston 132 and the bore section 113 may make partialcontact with each other during the sliding operation owing tofluctuations in shape and accuracy thereof. In Embodiment 1, because themolybdenum disulfide of the single molybdenum disulfide layer 160 has aproperty of being cleaved very easily, the shapes of the two matingmembers can be adapted to each other, and initial break-in is doneappropriately. As a result, the molybdenum disulfide of the singlemolybdenum disulfide layer 160 making contact with the surface of themating sliding member is abraded and adapted to the shape of thesurface. Therefore, sliding loss can be reduced, and it is possible toprovide a refrigerant compressor having high efficiency.

The relationship between freezing capacity and the amount of leakagefrom between the piston 132 and the bore section 113 will be describedbelow referring to FIG. 5.

The horizontal axis of FIG. 5 represents the clearance between thepiston 132 and the bore section 113, and the vertical axis representsthe freezing capacity.

According to the results shown in FIG. 5, when it is assumed that thespecified clearance is in the range of A to B μm, the freezing capacitylowers abruptly when the clearance exceeds B+4 μm.

Hence, the single molybdenum disulfide layer 160 on the sliding surfaceof the piston 132 is formed to have a thickness of 0.1 to 2.0 μm. Withthis configuration, even if the single molybdenum disulfide layer 160peels off during operation, the increase in the clearance between thepiston 132 and the bore section 113 is limited to 4.0 μm at the maximum.As a result, in the configuration of Embodiment 1, the amount of leakagefrom between the piston 132 and the bore section 113 does not increaseexcessively, and the freezing capacity is not reduced excessively. It isthus possible to provide a refrigerant compressor having stably higherefficiency.

Next, in the refrigerant compressor according to Embodiment 1 of thepresent invention, the effects of the single molybdenum disulfide layer160 and the mixed layer 150 formed on the sliding surface will bedescribed below.

When the piston 132 is positioned at the top dead center and at thebottom dead center, its speed becomes 0 m/s, no oil pressure isgenerated theoretically, and no oil film is formed. Hence, metalliccontact occurs frequently at the top dead center and the bottom deadcenter.

Furthermore, when the piston 132 of the refrigerant compressor ispositioned at the top dead center, the piston 132 receives a largecompression load due to the compressed high-pressure refrigerant. Thiscompression load is transmitted to the crankshaft 108 via the piston pin137 and the connecting rod 138, and the crankshaft 108 is pressed by thepiston 132 positioned near the top dead center and then tilted. Thistilting of the crankshaft 108 generates a force of tilting the piston132 inside the bore section 113. As a result, an end of the upper endface of the piston 132 on one side thereof and an end of the lower endface of the piston 132 on the other side thereof make contact with thebore section 113, and prying occurs. Because of this prying, the piston132 and the bore section 113 rub against each other, and abrasionoccurs. In the case of the refrigerant compressor having thecantilevered bearing according to Embodiment 1, the tilting of thecrankshaft 108 becomes large, and the prying occurs significantly.

As a result, the single molybdenum disulfide layer 160 is abraded, andthe mixed layer 150 is exposed on the surface and may be used as asliding face.

In Embodiment 1, the molybdenum disulfide of the mixed layer 150 has ahexagonal closed packing crystal structure, and the size of its moleculeis very small, approximately 6×10⁻¹⁴ μm. Hence the molybdenum disulfideis cleaved at a low friction coefficient. Therefore, even if metalliccontact occurs between the piston 132 and the bore section 113, thefriction coefficient of the sliding section becomes low, and the slidingloss is reduced. It is thus possible to provide a refrigerant compressorhaving high reliability.

FIG. 6 shows the concentration distribution of the molybdenum disulfideformed on the sliding surface of the piston 132 according to Embodiment1 of the present invention.

An energy dispersive X-ray analyzer is generally used to measure theconcentration of the molybdenum disulfide that is formed on the slidingface of the piston 132 and shown in FIG. 6. This energy dispersive X-rayanalyzer will be described below briefly.

Electrons emitted from the energy dispersive X-ray analyzer to thesliding surface of the piston 132 penetrate into the sliding surface toa certain depth, and a characteristic X-ray is generated. A vacancy isformed when an electron orbiting the atomic nucleus of an atom isejected outside from the atom by an electron having penetrated to thecertain depth, and an electron at a higher energy level makes atransition to the vacancy. At the time of the transition, excessiveenergy is generated as an X-ray being characteristic to each element,and the X-ray is referred to as the characteristic X-ray.

Because the energy dispersive X-ray analyzer can analyze the elementsconstituting the sliding surface of the piston 132 using thecharacteristic X-ray, the analyzer can measure the concentration of themolybdenum disulfide formed on the sliding surface. The maximumconcentration of the molybdenum disulfide in the mixed layer 150 isobtained near the most outer surface, and can be detected by measuringthe concentration near the most outer surface.

As shown in FIG. 6, the thickness of the mixed layer 150 containing themolybdenum disulfide is 0.1 to 2.0 μm, and its maximum concentration is5 to 20 wt %. When the molybdenum disulfide of the mixed layer 150described above is formed as described above, the self-lubrication ofthe molybdenum disulfide is stabilized, and the friction-coefficient isreduced further.

Next, the relationship between the maximum concentration of themolybdenum disulfide in the mixed layer 150 and the efficiency of therefrigerant compressor will be described below in detail referring toFIG. 7. FIG. 7 shows the relationship between the maximum concentrationof the molybdenum disulfide in the mixed layer 150 and the efficiency(C.O.P.: Coefficient of performance) of the refrigerant compressor. Therefrigerant compressor having been operated for a certain period wasused to obtain the relationship. As described above, the piston 132being tilted reciprocates inside the bore section 113, and an end of theupper end face of the piston 132 on one side thereof and an end of thelower end face of the piston 132 on the other side thereof make contactwith the bore section 113, and prying occurs. The mixed layer 150 of thepiston 132 serves as a sliding face.

As shown in FIG. 7, the efficiency of the refrigerant compressor risesabruptly when the maximum concentration of the molybdenum disulfide inthe mixed layer 150 exceeds 5 wt %. The efficiency of the refrigerantcompressor becomes almost constant when the maximum concentrationexceeds 15 wt %. Hence, it is conceived that the self-lubrication of themolybdenum disulfide is stabilized when the maximum concentration of themolybdenum disulfide in the mixed layer 150 is at least. 5 wt %.

On the other hand, for the purpose of raising the maximum concentrationof the molybdenum disulfide in the mixed layer 150, the particles of themolybdenum disulfide must be collided against a metallic sliding facefor a long time, that is, numerous particles must be collided. For thisreason, it is practical that the maximum concentration should remainapproximately 20 wt % in consideration of the cost and productivity ofthe molybdenum disulfide.

Hence, the maximum concentration of the molybdenum disulfide in themixed layer 150 according to Embodiment 1 is controlled between 5 to 20wt %.

In Embodiment 1 according to the present invention, the compressoroperating at a constant speed has been described above. As more and morerefrigerant compressors have been being driven using inverters in recentyears, the speeds of the refrigerant compressors become lower. In thecase of very slow operation at less than 20 Hz in particular, fluidlubrication is hardly attained, and metallic contact is apt to occur.For this reason, the effects of the present invention are furthersignificant.

It has been described that Embodiment 1 of the present invention isconfigured so that the mixed layer 150 is formed by solid-dissolvingmolybdenum disulfide in the sliding surface of the piston 132, and thesingle molybdenum disulfide layer 160 is further formed on the surfaceof the mixed layer 150. However, in the refrigerant compressor accordingto the present invention, the mixed layer 150 and the single molybdenumdisulfide layer 160 may be formed on the sliding surface of the boresection 113 or on the sliding surfaces of both the piston 132 and thebore section 113. By the use of the mixed layer 150 and the singlemolybdenum disulfide layer 160 formed on both the sliding members,higher abrasion resistance is obtained.

In Embodiment 1 of the present invention, the configuration wherein themixed layer 150 is formed by solid-dissolving molybdenum disulfide inthe sliding surface of the piston 132 and the single molybdenumdisulfide layer 160 is further formed on the surface of the mixed layer150 has been taken as an example and described in detail. However, evenif the mixed layer 150 and the single molybdenum disulfide layer 160 areformed at the sliding sections between the main shaft 109 of thecrankshaft 108 and the bearing section 114, between the flange face 120of the rotor 105 and the thrust washer 124, between the thrust section122 on the upper end face of the bearing section 114 and the thrustwasher 124, between the piston pin 137 and the connecting rod 138, andbetween the eccentric shaft 110 and the connecting rod 138, similarexcellent effects are obtained.

In Embodiment 1 of the present invention, the thrust bearing section 126comprising the flange face 120, the thrust section 122 and the thrustwasher 124 has been taken as an example and described. However, even ifthe thrust bearing comprises the thrust face 172 of the crankshaft 108,provided on the flange section 170 between the main shaft 109 and theeccentric shaft 110 of the crankshaft 108 on the opposite side of theeccentric shaft 110, and the thrust section 122 of the bearing section114, similar excellent effects are obtained.

In addition, the piston 181 shown in FIG. 8 is provided with aconnecting rod 183 to which a ball 182 is secured on the side connectedto the piston 181. The piston 181 is configured so that the ball 182 iscrimped so as to be freely movable in the piston 181. In the case of ajoint generally referred to as a ball joint, the amount of metalabrasion powder that enters the crimped free movement section and istrapped therein is reduced. Hence the free movement cannot berestricted, and high efficiency obtained immediately after productioncan be maintained.

A resin member 184 is held between the piston 181 and the ball 182 as anintervening member that is used to ensure smooth sliding therebetween asshown in FIG. 8.

A capillary tube 188 is used for the expander of a householdrefrigerator shown in FIG. 9. For the purpose of obtaining the four-starperformance according to Japanese Industrial Standards (JIS) andmaintaining the temperature of the freezer compartment at −18° C., theamount of decompression in the capillary tube 188 is increased, that is,the inside diameter thereof is designed so as to be less than 1 mm, sothat the temperature of the evaporator 196 is approximately −30° C.Adhesion of foreign substances to minute paths as typified by thecapillary tube 188 and to refrigerant paths inside the high-temperaturecompressor 197 becomes a major cause of reduction in cooling capacity.For this reason, intrusion of foreign substances is strictly limitedduring the production of household refrigerators, consumer durableshaving a service life of 10 or more years. Hence, regulations areenforced with respect to the purity of refrigerant and oil, and withrespect to residual moisture, metalworking oil, etc. Furthermore,because residual air becomes a cause of occurrence of foreign substancesowing to oxidation, vacuuming is carried out to attain high vacuum, andrefrigerant is hermetically sealed.

Next, the flow of the refrigerant will be described below. Therefrigerant is compressed using the compressor 197 and passes throughthe condenser 198, and the heat of the refrigerant is radiated. Then,the refrigerant is decompressed using the capillary tube 188, the heatinside the refrigerator 199 is absorbed using the evaporator 196, andthe refrigerant returns to the compressor 197.

The refrigerant flows complicatedly in a state of gas-liquid mixedcurrent at the entrance (not shown) and the exit (not shown) of thecapillary tube. Hence, foreign substances that are hard to be dissolvedin oil adhere generally to the entrance and the exit, therebyrestricting the circulation of the refrigerant. In the householdrefrigerator 195 according to Embodiment 1, because intrusion of foreignsubstances during production is strictly limited, adhesion of foreignsubstances to the entrance and the exit of the capillary tube, describedabove, rarely occurs. In addition, the amount of metal abrasion powderin the household refrigerator configured as described above is small.Hence, the amounts of metallic salts formed by the reaction between themetal abrasion powder and degraded oil and adhering to the refrigerantpaths are reduced, and foreign substances adhering to the refrigerantpaths can be limited very strictly. Therefore, the circulation amount ofthe refrigerant is not reduced, and it is possible to provide ahousehold refrigerator having high reliability.

Furthermore, although the capillary tube 188 is used in Embodiment 1,even when the expansion valve 189, an example of which is shown in FIG.10, is used, the restriction of the circulation of the refrigerant owingto foreign substances adhering to the valve seat face 190 thereof can beprevented, and excellent effects can be obtained.

Embodiment 2

FIG. 11 is a sectional view showing a refrigerant compressor accordingto Embodiment 2 of the present invention, FIG. 12 is a sectional viewtaken on line C-D in FIG. 11, and FIG. 13 is a magnified view of portionE in FIG. 12.

In FIGS. 11, 12 and 13, a closed container 201 accommodates an electricdriving element 204 comprising a stator 202 and a rotor 203, and arolling-piston-type compression element 205 driven using the electricdriving element 204, together with oil 206.

The compression element 205 comprises a shaft 210 having an eccentricsection 207, a main shaft section 208 and an auxiliary shaft section209; a cylinder 212 in which a compression chamber 211 is formed; a mainbearing 213 and an auxiliary bearing 214 that are used to seal both endfaces of the cylinder 212 and to journal the main shaft section 208 andthe auxiliary shaft section 209, respectively; a rolling piston 215 thatis loosely fitted on the eccentric section 207 and rolls inside thecompression chamber 211; and a plate-shaped vane 216 that is pressedagainst the rolling piston 215 and is used to partition the compressionchamber 211 into the high-pressure side and the low-pressure sidethereof. The rotor 203 is secured to the main shaft section 208

An oil pump 217 secured to the auxiliary bearing 214 comprises an oilsupply pipe 220 and an oil supply spring 222 loosely fitted in this oilsupply pipe 220. The oil pump 217 supplies the oil 206 to each of thesliding sections formed between the eccentric section 207 and therolling piston 215, between the main shaft section 208 and the mainbearing 213, and between the auxiliary shaft section 209 and theauxiliary bearing 214.

In Embodiment 2, a mixed layer 224 is formed by solid-dissolvingmolybdenum disulfide in the sliding surfaces of the eccentric section207, the main shaft section 208 and the auxiliary shaft section 209 ofthe shaft 210, that is, the surface of an iron-based (Fe-based) materialserving as the base material thereof, and a single molybdenum disulfidelayer 228 is further formed on the surface of the mixed layer 224.

It is preferable that the purity of the molybdenum disulfide should be98% or more, that the thickness of the single molybdenum disulfide layer228 should be 0.1 to 2.0 μm, that the thickness of the mixed layer 224should be 0.1 to 2.0 μm, and that the maximum concentration of themolybdenum disulfide in the mixed layer 224 should be 5 wt % or more and50 wt % or less.

The operation of the refrigerant compressor according to Embodiment 2configured as described above will be described below.

As the rotor 203 is rotated, the shaft 210 is rotated, and the rollingpiston 215 loosely fitted in the eccentric section 207 rolls inside thecompression chamber 211. Hence, the volumes of the high-pressure sidechamber and the low-pressure side chamber of the compression chamber 211are changed continuously, whereby refrigerant gas is compressedcontinuously. Furthermore, the compressed refrigerant gas is dischargedinto the closed container 201, and high-pressure atmosphere is createdinside the closed container 201. Moreover, because the pressure insidethe closed container 201 is high, the atmospheric pressure inside theclosed container 201 acts as a back pressure for the vane 216 andpresses the tip of the vane 216 against the outer circumferentialsurface of the rolling piston 215.

Additionally, as the shaft 210 is rotated, the oil supply spring 222loosely fitted in the oil supply pipe 220 continuously supplies the oil206 to the respective sliding sections.

In the rolling-piston-type refrigerant compressor, the rolling piston215 is loosely fitted on the eccentric section 207 so as to berotatable. Hence, the relative speed between the rolling piston 215 andthe eccentric section 207 is lower than the relative speed between themain shaft section 208 and the main bearing 213 and the relative speedbetween the auxiliary shaft section 209 and the auxiliary bearing 214.This means that Sommerfeld number S (Expression 1) that indicates thecharacteristic of a journal bearing and is obtained using the radius R,the radial clearance C and the speed N of the bearing, the viscosity uof oil, and the face pressure P of the bearing becomes small, resultingin a disadvantageous condition in which a metallic contact is apt tooccur during sliding lubrication.

S=μ×N/P×(R/C)²  (Expression 1)

In the rolling-piston-type refrigerant compressor, a condensationpressure is generally created inside the closed container 201, its innerpressure is high, and the refrigerant is apt to be dissolved in the oil206. As a result, the viscosity of the oil is lowered, and theabove-mentioned Sommerfeld number S (Expression 1) indicating thecharacteristic of the journal bearing becomes small, resulting in adisadvantageous condition during sliding lubrication.

However, the mixed layer 224 is formed by solid-dissolving molybdenumdisulfide in the sliding surfaces of the eccentric section 207, the mainshaft section 208 and the auxiliary shaft section 209 of the shaft 210,and the single molybdenum disulfide layer 228 is further formed on thesurface of the mixed layer 224. With this configuration, even in thedisadvantageous condition wherein Sommerfeld number S (Expression 1)becomes small during sliding lubrication, the molybdenum disulfide ofthe single layer 228 has a property of being cleaved very easily. Hence,the shapes of the two mating members can be adapted to each other, andinitial break-in is done appropriately. As a result, the molybdenumdisulfide of the single molybdenum disulfide layer 228 making contactwith the surface of the mating member is abraded and adapted to theshape of the surface. Therefore, the sliding loss of therolling-piston-type refrigerant compressor can be reduced, and it ispossible to provide a refrigerant compressor having high efficiency.

Furthermore, even if the single molybdenum disulfide layer 228 isabraded and peels off owing to metallic contact between the slidingmembers, the molybdenum disulfide of the mixed layer 224 has a hexagonalclosed packing crystal structure, and the size of its molecule is verysmall, approximately 6×10⁻¹⁴ μm. Hence the molybdenum disulfide iscleaved at a low friction coefficient. Therefore, even if metalliccontact occurs between the rolling piston 215 and the eccentric section207, between the main shaft section 208 and the main bearing 213, andbetween the auxiliary shaft section 209 and the auxiliary bearing 214,the friction coefficient of the sliding section becomes low, and thesliding loss is reduced. Therefore, with the configuration of Embodiment2, it is possible to provide a refrigerant compressor having highreliability.

Moreover, the thickness of the mixed layer 224 is set at 0.1 to 2.0 μm,and the maximum concentration of molybdenum disulfide in the mixed layer224 is set at 5 wt % or more and 20 wt % or less. Hence, theself-lubrication of the molybdenum disulfide is stabilized, and thefriction coefficient is reduced further. Therefore, with theconfiguration described above, it is possible to provide a refrigerantcompressor having high reliability and high efficiency.

In Embodiment 2 of the present invention, the mixed layer 224 is formedby solid-dissolving molybdenum disulfide in the sliding surfaces of theeccentric section 207, the main shaft section 208 and the auxiliaryshaft section 209, and the single molybdenum disulfide layer 228 isfurther formed on the surface of the mixed layer 224. However, the mixedlayer 224 and the single molybdenum disulfide layer 228 may be formed onthe inner circumferential surface of the rolling piston 215, and thesurfaces of the main bearing 213 and the auxiliary bearing 214.Furthermore, the mixed layer 224 and the single molybdenum disulfidelayer 228 may be formed on both of the surface of the eccentric section207 and the inner circumferential surface of the rolling piston 215,both the surfaces of the main shaft section 208 and the main bearing213, and both the surfaces of the auxiliary shaft section 209 and theauxiliary bearing 214. By the use of the mixed layer 224 and the singlemolybdenum disulfide layer 228 formed on the surfaces of both thesliding members, it is possible to obtain an excellent effect capable ofproviding a refrigerant compressor having high reliability and highefficiency.

Furthermore, in the case that the mixed layer 224 is formed bysolid-dissolving molybdenum disulfide in the sliding surfaces of thesliding members in the sliding sections between the rolling piston 215and the vane 216, between the main bearing 213 and the vane 216, betweenthe auxiliary bearing 214 and the vane 216, between the main bearing 213and the rolling piston 215, between the auxiliary bearing 214 and therolling piston 215, between the cylinder 212 and the vane 216, betweenthe cylinder 212 and the rolling piston 215, and between the oil supplypipe 220 and the oil supply spring 222, and that the single molybdenumdisulfide layer 228 is further formed on the surface of the mixed layer224, the friction coefficient at each sliding section is reduced, and itis possible to provide a refrigerant compressor having high reliabilityand high efficiency.

In Embodiment 2 according to the present invention, a compressoroperating at a constant speed has been described above. As more and morerefrigerant compressors have been being driven using inverters in recentyears, the speeds of the refrigerant compressors become lower. In thecase of very slow operation at less than 20 Hz in particular, theproblem of abnormal abrasion becomes more serious. For this reason, theeffects of the present invention are further significant.

INDUSTRIAL APPLICABILITY

As described above, in the refrigerant compressor according to thepresent invention, the mixed layer is formed by solid-dissolvingmolybdenum disulfide in the sliding surface of a sliding component, andthe single molybdenum disulfide layer is further formed on the surfacesof the mixed layer. Hence, the friction coefficient of the slidingsurface is reduced, and it is possible to provide a compressor havinghigh reliability and high efficiency. The present invention is thuswidely applicable to apparatuses having a refrigerating cycle.

1. A refrigerant compressor wherein a compression element comprisessliding components made of metallic materials, and a mixed layer isformed by solid-dissolving molybdenum disulfide in at least one of thesliding faces of said sliding components, and a single molybdenumdisulfide layer is further formed on the surface of said mixed layer. 2.The refrigerant compressor according to claim 1, wherein the maximumconcentration of the molybdenum disulfide in said mixed layer is 5 wt %or more.
 3. The refrigerant compressor according to claim 1, wherein thethickness of said mixed layer is 0.1 to 2.0 μm.
 4. The refrigerantcompressor according to claim 1, wherein the purity of the molybdenumdisulfide of said single molybdenum disulfide layer is 98% or more. 5.The refrigerant compressor according to claim 1, wherein the thicknessof said single molybdenum disulfide layer is 0.1 to 2.0 μm.
 6. Therefrigerant compressor according to claim 1, wherein oil is accumulatedand a compression element is accommodated in a closed container, saidcompression element is a reciprocating compression element comprising acrankshaft equipped with a main shaft and an eccentric shaft; a thrustsection, one end of which is integrated with said crankshaft and theother end of which is integrated with a bearing section; said bearingsection rotatably journaling said main shaft; a cylinder block in whicha cylindrical bore section is formed; a piston reciprocating inside saidcylindrical bore section; a piston pin disposed in parallel with saideccentric shaft and secured to said piston; and a connecting rod forconnecting said eccentric shaft to said piston, and said slidingcomponent made of a metallic material is at least either one of saidcrankshaft, said thrust section, said cylinder block, said piston, saidpiston pin, and said connecting rod.
 7. The refrigerant compressoraccording to claim 1, wherein oil is accumulated and a compressionelement is accommodated in a closed container, said compression elementcomprises a crankshaft equipped with a main shaft and an eccentricshaft; a thrust section, one end of which is integrated with saidcrankshaft and the other end of which is integrated with a bearingsection; said bearing section rotatably journaling said main shaft; acylinder block in which a cylindrical bore section is formed; a pistonreciprocating inside said cylindrical bore section; and a connecting rodto which a ball is secured on the side connected to said piston, saidpiston in which said ball is movably held by crimping constitutes areciprocating compression element, and said sliding component made of ametallic material is at least either one of said crankshaft, said thrustsection, said cylinder block, said piston, and said connecting rod. 8.The refrigerant compressor according to claim 1, wherein oil isaccumulated and a compression element is accommodated in a closedcontainer, said compression element is a rolling-piston-type compressionelement comprising a shaft having an eccentric section; a cylinder inwhich a compression chamber is formed in coaxial with the rotationcenter of said shaft; a rolling piston that is loosely fitted on saideccentric section and rolls inside said compression chamber; a vane thatpartitions said compression chamber into the high-pressure side and thelow-pressure side thereof when made contact with said rolling pistonunder pressure; a main bearing and an auxiliary bearing that are used toseal both end faces of said cylinder and to journal said shaft on theside of an electric driving element and on the opposite side of saidelectric driving element, respectively; an oil supply spring secured toone end of said shaft; and an oil supply pipe that accommodates said oilsupply spring and one end of which is open and immersed in said oil, andsaid sliding component made of a metallic material is at least eitherone of said shaft, said cylinder, said rolling piston, said vane, saidmain bearing, said auxiliary bearing, said oil supply spring, and saidoil supply pipe.
 9. A cooling system comprising said refrigerantcompressor according to claim 1, and an expander equipped with either acapillary tube or an expansion valve.
 10. A refrigerator having acooling system comprising said refrigerant compressor according to claim1, and an expander equipped with either a capillary tube or an expansionvalve.